Revista internacional de contaminación ambiental
Print version ISSN 0188-4999
GONZALEZ-FLORES, Eduardo et al. Fractionation and bioavailability of heavy metals in agricultural soils amended with municipal biosolids. Rev. Int. Contam. Ambient [online]. 2011, vol.27, n.4, pp. 290-301. ISSN 0188-4999.
The biosolids originated in the treatment of municipal wastewater are used in agricultural soils as a source of nutrients and organic matter. Heavy metal content may restrict their use as agricultural amendment, due to the potential risk of introducing them into food webs. To determine the total concentration of heavy metals in soils amended with biosolids is an insufficient criterion for assessing this risk. Heavy metals are bound to different solids components of soil, which according to their different physicochemical characteristics have different availability. The aim of this study was to determine distribution and bioavailable concentrations of Cd, Cu, Ni, Pb, and Zn in soil amended with biosolids in a period of six years and a possible relationship between the bioavailability and distribution of metals with the age of application. It was used a sequential chemical extraction procedure of four steps for determining the concentrations of Cd, Cu, Ni, Pb, and Zn in four operationally defined chemical fractions that represent the bioavailability and distribution of metals in the amended soils. The total concentrations were determined by an open system acid digestion. The quantification of heavy metals was performed by ICP-AES. The Cd was not detected. The bioavailability of Cu and Pb decreases with age of application and Zn increases. The age of application of biosolids influenced the redistribution of Cu, Pb, and Zn in the four extracted fractions. The distribution of Ni is less affected by the age of application of biosolids. The metals studied are held in a high percentage in the more stable fractions, oxidizable and residual. The bioavailable fraction of each metal shows low percentages, indicating low availability in the soil and therefore a low risk of being incorporated into food webs.
Keywords : speciation; sequential chemical extraction; sewage sludge; trace elements.